Fig. 6. Gill Na⁺/K⁺-ATPase activity in trout held in freshwater (Pre) and following transfer to freshwater (filled circles), 40% seawater (open squares) and 80% seawater (filled triangles). Vertical broken line represents the abrupt transfer. Symbols are offset for clarity where necessary. Data are means ± S.E.M. (N=8). Asterisks indicate significant difference from the control (freshwater) value.